1. Field of the Invention
This invention relates generally to cover assemblies for receptacles and the like and more particularly to an improved cover assembly of this class embodying a cover supporting base having an opening, a removable cover for closing the base opening, and a novel releasable locking mechanism for locking the cover to the base. The invention also provides a novel cover for the cover assembly.
2. Discussion of the Prior Art
It will become evident as the description proceeds that the improved cover assembly of this invention may be used for a variety of purposes. The cover assembly is primarly intended, however, for use as a closure for wells of the kind which are utilized at hazzardous fluid handling facilities, particularly motor vehicle service stations, to service underground storage tanks, that is fill the tanks and vent vapors from the tanks. Such underground tank servicing wells are used at motor vehicle service stations to contain the upper capped ends of the fill tubes and vent tubes leading to underground fuel storage tanks and, in many cases, associated valves, electrical equipment, pumps, and the like. The cover assembly will be described in the context of this service station use.
An underground fuel storage tank of the kind installed at motor vehicle service stations has an underground tank proper and a fill tube extending to ground level through which the tank is filled with the fuel to be stored. A vent tube also extends from the tank to ground level through which fuel vapor may be vented from the tank. These fill and vent tubes have upper open ends which are normally sealed by removable caps. A typical motor vehicle service station has several such underground fuel storage tanks. The upper capped ends of the tank fill and vent tubes are generally situated within a storage tand servicing well recessed into a concrete apron or other finished ground level surface in such a way as to enable easy access to the capped ends of the tubes and yet shield these ends against damage by surface traffic. A service station underground fuel tank is filled from a fuel delivery tank truck through a delivery hose which is coupled to the open end of the tank fill tube after removal of the cap from the fill tube. The upper end of the vent tube is connected to the delivery truck through a vapor hose through which fuel vapor displaced from the tank during filling is conducted back to the delivery truck.
When filling a service station fuel tank, a small amount of fuel spillage commonly occurs, particularly during coupling and uncoupling of the delivery hose from the tank fill tube. This spillage may be due to either or both leakage at the coupling between the hose and the fill tube and draining of standing liquid from the hose during coupling and uncoupling of the hose to and from the fill tube A few years ago, this fuel spillage problem was dealt with by simply hosing off the fuel from surface onto which the spill had occurred. Later environmental legislation made this practice illegal and mandated the use of so-called spill containment devices to collect any fuel spillage. The service station tank servicing wells referred to above serve such a spill containment function. Examples of existing spill containment devices wells are disclosed in the following patents:
U.S. Pat. No. 4,593,714 dated Jan. 10, 1986 to Madden. PA1 U.S. Pat. No. 4,762,440 dated Aug. 9, 1988 to Argandona. PA1 U.S. Pat. No. 4,842,443 dated Jan. 27, 1989 to Argandona.
An underground tank servicing well must satisfy other requirements in addition to the basic fuel spillage contaiment requirements mentioned above. One of these additional requirements resides in the fact that the well, when not in use for filling an underground fuel storage tank, must be closed by a removable cover which is sealed to the lower body of the well in such a way as to prevent entrance of water and other substances into the well. This is particularly important during a rainstorm, or when hosing off the surface about the well, or during melting of snow or ice on the surface. A cover must provide sealing against the entrance of water into the well. Water entering an underground fuel storage tank, as by leakage from the surface, prevents a serious problem. Upon entering a storage tank, water drops to the bottom of the tank, being heavier than gasoline. It is then the first liquid drawn from the bottom of the tank by the pumping system, and is transferred via dispensing pumps into vehicle tanks. Water in gasoline supplied to engine fuel injectors can effectively ruin the injectors and require expensive repairs. The removal of water from a storage tank involves substantial expense, such as $1.50 per gallon, for pumping out the water and transporting it to disposal.
The spill containment devices described in the patents mentioned above are somewhat deficient because they lack means for positively clamping their covers in fluid sealing relation to their spill containers. As a result, only gravity holds the covers closed, and it is possible that gravity may not be sufficient to cause the covers to seal properly to the spill containers. Also, the covers of the patented spill containers are vunerable to being accidentally dislodged by passage of a vehicle or snow plow over the covers.
Positively locking covers for various purposes are known, of course. One such cover is a removable cap assembly for closing the open end of a pipe, such as the open end of a storage tank fill tube. This locking cap assembly includes a cap proper and a releasable locking mechanism on the cap. The cap has an outer circular end wall and an inner annular rim projecting axially beyond the inner side of the end wall. The cap is designed to fit over the open end of a pipe having an external circumferential groove forming an annular shoulder facing axially of and away from the open end of the pipe. The cap locking mechanism includes a pair of diametrically opposed locking levers pivoted between their ends on the cap at its circumference on parallel pivot axes transverse to the axis of the cap. These locking levers extend along diametrically opposite sides of the cap externally of the cap and have axially outer ends extending axially of the cap beyond the axially outer side of the cap end wall and axially inner, radially inwardly directed hook-shaped ends extending axially of the cap beyond the axially inner end to the cap rim. The outer ends of the locking levers are joined by a pair of links which extend across the axially outer side of the cap end wall. These links have adjacent radially inner ends pivotally connected to one another and to a lock handle and distal radially outer ends pivotally connected to the axially outer ends of the locking levers.
When the cap is placed over the end of the pipe, inward locking movement of the lock handle axially of the cap and toward its end wall rotates the outer ends of the locking levers radially outward and therey rotates the inner hook-shaped ends of the arm radially inward to locking positions in which they engage the shoulder on the pipe to lock the cap to the pipe. The two links form a toggle joint between the levers whose adjacent end pivot moves past center to lock the levers in their locking positions during locking movement of the lock handle.